(undefined method `belongs_to' for ListItem:Class [NoMethodError])

Hi,

I'm implementing the example in the agile web development with rails.
In the Order line_item Product relationship setting.
I got the error while include "belongs to :product" in line_item.rb

And I found
http://rubyforge.org/pipermail/nitro-general/2005-August/000934.html

about a patch that fix the problem

ANyone knows if there is anyway to fix it without this old patch?

THX